Ink jet ink set

ABSTRACT

A color set for forming an ink jet image comprising:  
     at least two color inks, each ink comprising a carrier and a pigment;  
     wherein the Relative Gloss Variability (RGV) (Equation A) among inks is less than 10%; when 60° is used as the specular angle.  
                     RGV        (   %   )       =           ∑     I   =   1     N               (         Gloss        (     Imaged                 Area     )       I     -   AG     )            AG     N               Where             AG   =         ∑     I   =   1     N            Gloss        (     Imaged                 Area     )       I       N                   Equation                   (   A   )                         
 
     I is a variable which identifies a certain color patch used in the evaluation,  
     N is the total number of color patches used in the evaluation.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application relates to commonly assigned copendingapplication Ser. No. ______(Docket No. 83866)entitled INK JET INKSET/RECEIVER COMBINATION; application Ser. No. ______ (Docket No.83899), entitled A METHOD OF SELECTING INK JET INKS IN A COLOR SET;application Ser. No. ______(Docket No. 83900) entitled A METHOD OFSELECTING INK JET INKS IN A COLOR SET and application Ser. No.______(Docket No. 83901) entitled INK JET INK SET/RECEIVER COMBINATIONfiled simultaneously herewith. These copending applications areincorporated by reference herein for all that they contain.

FIELD OF THE INVENTION

[0002] This invention relates to inks for ink jet printing that provideimages with improved inter-color gloss differences.

BACKGROUND OF THE INVENTION

[0003] Ink jet printing is a non-impact method for producing images bythe deposition of ink droplets in a pixel-by-pixel manner to animage-recording element in response to digital signals. There arevarious methods which may be utilized to control the deposition of inkdroplets on the image-recording element to yield the desired image. Inone process, known as continuous ink jet, a continuous stream ofdroplets is charged and deflected in an imagewise manner onto thesurface of the image-recording element, while unimaged droplets arecaught and returned to an ink sump. In another process, known asdrop-on-demand ink jet, individual ink droplets are projected as neededonto the image-recording element to form the desired image. Commonmethods of controlling

[0004] The inks used in the various ink jet printers can be classifiedas either dye-based or pigment-based. A dye is a colorant, which isdissolved in the carrier medium. A pigment is a colorant that isinsoluble in the carrier medium, but is dispersed or suspended in theform of small particles, often stabilized against flocculation andsettling by the use of dispersing agents. The carrier medium can be aliquid or a solid at room temperature in both cases. Commonly usedcarrier media include water, mixtures of water and organic co-solventsand high boiling organic solvents, such as hydrocarbons, esters,ketones, etc

[0005] Although there have been many recent advances in the art ofdye-based ink jet inks, such inks still suffer from major deficienciessuch as poor image stability against light and gases commonly containedin the air, such as ozone (O3), nitrogen oxide (NOx) and sulfur oxide(SOx), especially on receivers having porous ink receiving layers. Onemethod of addressing these limitations is to use pigment-based inks.When designed properly, pigment based inks usually can demonstrate imagestability significantly higher than the dye based inks, and moreimportantly, approaching the archival quality as compared to silverhalide photographic prints.

[0006] A major image quality drawback of pigment-based inks is“inter-color differential gloss”, where the gloss levels of imaged areasof different colors are very different from each other. This type ofimage quality defect can be quite noticeable, even to ordinaryobservers. One possible solution to this problem is to cover the entirereceiver with a protective layer through techniques such as laminatingthe printed image, or fusing the top fusible polymeric layer inreceivers to a continuous overcoat layer, such as those disclosed inU.S. patent application, Ser. No.09/954,779, filed on Sep. 18, 2001 ofWexler, or coating a protective layer on the imaged areas as describedin EP1057646 and EP1048466. However, all these approaches involveseparate steps after printing, making the entire process complex andcostly.

[0007] What the art needs is a way to minimize gloss level variationsamong different colors in a color image when the various inks aredeposited and dried on a receiver. This should be done as part of theprinting process and not as a separate step after printing.

SUMMARY OF THE INVENTION

[0008] The present invention provides an inkjet color ink set capable ofproducing images wherein the gloss level variations among differentcolors in the color image is minimized. The gloss variation is judgedafter the ink is deposited and dried on a receiver, but the invention isa part of the ink selection and printing process; not a separate stepafter printing.

[0009] In accordance with the invention, the gloss level of each ink ispredetermined, as measured from single color patches on a receiver, andthe gloss level variability among different inks is calculated. Bykeeping the gloss variability with a certain range, the quality of theimage is improved. Hence, the present invention discloses a color setfor forming an ink jet image comprising: at least two color inks, eachink comprising a carrier and a pigment; wherein the Relative GlossVariability (RGV) (Equation A) among inks is less than 10%; when 60° isused as the specular angle. $\begin{matrix}\begin{matrix}{{{RGV}(\%)} = \frac{\frac{\sum\limits_{I = 1}^{N}{\left( {{{Gloss}\left( {{Imaged}\quad {Area}} \right)}_{I} - {AG}} \right)}}{AG}}{N}} \\{Where} \\{{AG} = \frac{\sum\limits_{I = 1}^{N}{{Gloss}\left( {{Imaged}\quad {Area}} \right)}_{I}}{N}}\end{matrix} & {{Equation}\quad (A)}\end{matrix}$

[0010] I is a variable which identifies a certain color patch used inthe evaluation,

[0011] N is the total number of color patches used in the evaluation.

[0012] The advantage of the invention is that it minimizes glossdifference among the different colors in a printed color image and thisis done as a part of the initial printing process.

DETAILED DESCRIPTION OF THE INVENTION

[0013] Gloss Definition

[0014] Gloss, commonly referred to as specular gloss, of a surface isdefined as its degree of approach to a mirror-like surface. It is ameasure of the amount of energy reflected at a reflection angle equal toor near the angle of incidence. Specular gloss can be measured in termsof gloss units (gu), at several angles, e.g. 20°, 30°, 45°, 60°, 75° and80° from the surface normal. Gloss meters are used to measure the glossof a sample at various angles. The BYK-Gardner micro-TRI-glossmeter isan example of such an instrument. The particular instrument used in thepresent invention is capable of measuring gloss at three angles, 20°,60° and 85°.

[0015] When inks are printed on a receiver, the gloss level of theprinted image is determined by both ink and receiver. Ink properties,such as, for example, the refractive index of polymers in the inks, thefilm forming property of the polymers in the inks after printing, andthe ink load deposit on the receiver, may individually or in combinationinfluence the gloss of a printed image. In the present invention, it isdisclosed that for pigment-based inks, pigment particle size anddistribution, together with the use of non-film forming particles canhave a significant impact on the gloss levels. The present inventorshave further discovered that by keeping the gloss level variabilityamong different inks with a certain range, the printed images have lessobservable inter-color gloss difference, thus to improve the imagequality of the overall print.

[0016] In this invention, the inter-color gloss difference ischaracterized by a parameter called Relative Gloss Variability (RGV %),which is derived from Average Gloss (AG) as defined in Equation A.$\begin{matrix}\begin{matrix}{{{RGV}(\%)} = \frac{\frac{\sum\limits_{I = 1}^{N}{\left( {{{Gloss}\left( {{Imaged}\quad {Area}} \right)}_{I} - {AG}} \right)}}{AG}}{N}} \\{Where} \\{{AG} = \frac{\sum\limits_{I = 1}^{N}{{Gloss}\left( {{Imaged}\quad {Area}} \right)}_{I}}{N}}\end{matrix} & {{Equation}\quad (A)}\end{matrix}$

[0017] I is a variable which identifies a certain color patch used inthe evaluation,

[0018] N is the total number of color patches used in the evaluation.

[0019] In this invention, RGV is obtained based on the followingprocedure: load the selected color ink sets into a printer and printonto a receiver using a test image. The test image is designed toconsist of single color patches of Dmax density (100% dot coverage). Thesize of the patch needs to be large enough, for example, approximately 3by 3 centimeters in size for uniform gloss measurement. The dot coverageis also important in order to minimize the gloss contribution from barereceiver resulted from the non-ink coverage at the pixel level. Usually,a reflection density of 1.5 (Dmax) can be achieved at 100% dot coverage.The color used in the evaluation may include any combination of colorscapable of being generated by the selected ink set, such as primarycolors (for example, cyan, magenta, yellow, black) or, optionalsecondary colors (for example, red, green, blue), process black (acombination of cyan, magenta and yellow) or 400% black (a combination ofcyan, magenta, yellow and black). After allowing the printed test imagesto dry for 24 hours at ambient temperature and humidity, the gloss levelat a certain specular angle (for example, 60 degree) of each color patchis then measured, using a gloss meter, for example, the BYK-Gardnermicro-TRI-glossmeter.

[0020] It is preferred that the ink set is capable of generating RGVvalue among inks of less than 10% (when 60 degree is used as thespecular angle). It is further preferred that the ink set is capable ofgenerating RGV value among inks of less than 7% (when 60 degree is usedas the specular angle). It is more preferred that the ink set is capableof generating RGV value among inks of less than 5% (when 60 degree isused as the specular angle).

[0021] Pigment Milling and Ink Formulation

[0022] The process of preparing inks from pigments commonly involves twosteps: (a) a dispersing or milling step to break up the pigment to theprimary particle, and (b) a dilution step in which the dispersed pigmentconcentrate is diluted with a carrier and other addenda to a workingstrength ink. In the milling step, the pigment is usually suspended in acarrier (typically the same carrier as that in the finished ink) alongwith rigid, inert milling media. Mechanical energy is supplied to thispigment dispersion, and the collisions between the milling media and thepigment cause the pigment to deaggregate into its primary particles. Adispersant or stabilizer, or both, is commonly added to the pigmentdispersion to facilitate the deaggregation of the raw pigment, tomaintain colloidal particle stability, and to retard particlereagglomeration and settling.

[0023] There are many different types of materials that may be used asmilling media, such as glasses, ceramics, metals, and plastics. In apreferred embodiment, the grinding media can comprise particles,preferably substantially spherical in shape, e.g., beads, consistingessentially of a polymeric resin. In general, polymeric resins suitablefor use as milling media are chemically and physically inert,substantially free of metals, solvent and monomers, and of sufficienthardness and firability to enable them to avoid being chipped or crushedduring milling. Suitable polymeric resins include crosslinkedpolystyrenes, such as polystyrene crosslinked with divinylbenzene,styrene copolymers, polyacrylates such as poly(methyl methylacrylate),olycarbonates, polyacetals, such as Derlin™, vinyl chloride polymers andcopolymers, polyurethanes, polyamides, poly(tetrafluoroethylenes), e.g.,Teflon™, and other fluoropolymers, high density polyethylenes,polypropylenes, cellulose ethers and esters such as cellulose acetate,poly(hydroxyethylmethacrylate), poly(hydroxyethylacrylate), siliconecontaining polymers such as polysiloxanes and the like. The polymer canbe biodegradable. Exemplary biodegradable polymers includepoly(lactides), poly(glycolids) copolymers of lactides and glycolide,polyanhydrides, poly(imino carbonates), poly(N-acylhydroxyproline)esters, poly(N-palmitoyl hydroxyprolino) esters, ethylene-vinyl acetatecopolymers, poly(orthoesters), poly(caprolactones), andpoly(phosphazenes). The polymeric resin can have a density from 0.9 to3.0 g/cm3. Higher density resins are preferred in as much as it isbelieved that these provide more efficient particle size reduction. Mostpreferred are crosslinked or uncrosslinked polymeric media based onstyrene.

[0024] Milling can take place in any suitable grinding mill. Suitablemills include an air jet mill, a roller mill, a ball mill, an attritormill and a bead mill. A high speed mill is preferred. By high speed millwe mean milling devices capable of accelerating milling media tovelocities greater than about 5 meters per second. Sufficient millingmedia velocity is achieved, for example, in Cowles-type saw toothimpeller having a diameter of 40 mm when operated at 9,000 rpm. Thepreferred proportions of the milling media, the pigment, the liquiddispersion medium and dispersant can vary within wide limits anddepends, for example, up on the particular material selected and thesize and density of the milling media etc. After milling is complete,the dispersion of active material is separated from the grinding mediaby simple sieving or filtration. With either of the above modes thepreferred amounts and ratios of the ingredients of the mill grind willvary widely depending upon the specific materials and the intendedapplications. The contents of the milling mixture comprise the millgrind and the milling media. The mill grind comprises pigment,dispersant and a liquid carrier such as water. For aqueous ink jet inks,the pigment is usually present in the mill grind at 1 to 50 weight %,excluding the milling media. The weight ratio of pigment to dispersantis 20:1 to 1:2. The high speed mill is a high agitation device, such asthose manufactured by Morehouse-Cowles, Hockmeyer et al.

[0025] The dispersant is another important ingredient in the mill grind.Preferred dispersants used in the present invention include sodiumdodecyl sulfate, acrylic and styrene-acrylic copolymers, such as thosedisclosed in U.S. Pat. Nos. 5,085,698 and 5,172,133, and sulfonatedpolyesters and styrenics, such as those disclosed in U.S. Pat. No.4,597,794. Other patents referred to above in connection with pigmentavailability also disclose a wide variety of dispersant to select from.The dispersant used in the examples is potassium N-methyl-N-oleoyltaurate (K-OMT).

[0026] The milling time can vary widely and depends upon the pigment,mechanical means and residence conditions selected, the initial anddesired final particle size, etc. For aqueous mill grinds using thepreferred pigments, dispersants, and milling media described above,milling times will typically range from 1 to 100 hours. The milledpigment concentrate is preferably separated from the milling media byfiltration.

[0027] The pigment particles useful in the invention may have anyparticle sizes than can be jetted through a print head. Preferably, thepigment particles have a mean particle size of less than about 0.5micron.

[0028] A wide variety of organic and inorganic pigments, alone or incombination, may be selected for use in the present invention. Colorantparticles which may be used in the invention include pigments asdisclosed, for example in U.S. Pat. Nos. 5,026,427; 5,086,698;5,141,556; 5,160,370; and 5,169,436, the disclosures of which are herebyincorporated by reference. The exact choice of pigments will depend uponthe specific application and performance requirements such as colorreproduction and image stability. Pigments suitable for use in thepresent invention include, for example, azo pigments, monoazo pigments,disazo pigments, azo pigment lakes, β-Naphthol pigments, Naphthol ASpigments, benzimidazolone pigments, disazo condensation pigments, metalcomplex pigments, isoindolinone and isoindoline pigments, polycyclicpigments, phthalocyanine pigments, quinacridone pigments, perylene andperinone pigments, thioindigo pigments, anthrapyrimidone pigments,flavanthrone pigments, anthanthrone pigments, dioxazine pigments,triarylcarbonium pigments, quinophthalone pigments, diketopyrrolopyrrole pigments, titanium oxide, iron oxide, and carbon black. Typicalexamples of pigments which may be used include Color Index (C. I.)Pigment Yellow 1, 2, 3, 5, 6, 10, 12, 13, 14, 16, 17, 62, 65, 73, 74,75, 81, 83, 87, 90, 93, 94, 95, 97, 98, 99, 100, 101, 104, 106, 108,109, 110, 111, 113, 114, 116, 117, 120, 121, 123, 124, 126, 127, 128,129, 130, 133, 136, 138, 139, 147, 148, 150, 151,152, 153, 154, 155,165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 179,180, 181, 182, 183, 184, 185, 187, 188, 190, 191, 192, 193, 194; C. I.Pigment Orange 1, 2, 5, 6, 13, 15, 16, 17, 17:1, 19, 22, 24, 31, 34, 36,38, 40, 43, 44, 46, 48, 49, 51, 59, 60, 61, 62, 64, 65, 66, 67, 68, 69;C. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,17, 18, 21, 22, 23, 31, 32, 38, 48:1, 48:2, 48:3, 48:4, 49:1, 49:2,49:3, 50:1, 51, 52:1, 52:2, 53:1, 57:1, 60:1, 63:1, 66, 67, 68, 81, 95,112, 114, 119, 122, 136, 144, 146, 147, 148, 149, 150, 151, 164, 166,168, 169, 170, 171, 172, 175, 176, 177, 178,179, 181,184,185, 187,188,190, 192, 194, 200, 202, 204, 206, 207, 210, 211, 212, 213, 214,216, 220, 222, 237, 238, 239, 240, 242, 243, 245, 247, 248, 251, 252,253, 254, 255, 256, 258, 261, 264; COLOR INDEX Pigment Violet 1, 2, 3,5:1, 13, 19, 23, 25, 27, 29, 31, 32, 37, 39, 42, 44, 50; COLOR INDEXPigment Blue 1, 2, 9, 10, 14, 15:1, 15:2, 15:3, 15:4, 15:6, 15, 16, 18,19, 24:1, 25, 56, 60, 61, 62, 63, 64, 66; COLOR INDEX Pigment Green 1,2, 4, 7, 8, 10, 36, 45; COLOR INDEX Pigment Black 1, 7, 20, 31, 32, andCOLOR INDEX Pigment Brown 1, 5, 22, 23, 25, 38, 41, 42. In a preferredembodiment of the invention, the pigment is COLOR INDEX Pigment Blue15:3, COLOR INDEX Pigment Red 122, COLOR INDEX Pigment Yellow 155, COLORINDEX Pigment Yellow 74, bis(phthalocyanylalumino)tetraphenyldisiloxaneor COLOR INDEX Pigment Black 7.

[0029] The pigment used in element of the invention is present in theink jet ink in any effective amount, generally from about 0.1 to about10% by weight, and preferably from about 0.5% to about 6% by weight.

[0030] Typically, the aqueous carrier for the ink composition is wateror a mixture of water and at least one water miscible co-solvent.Selection of a suitable mixture depends on requirements of the specificapplication, such as desired surface tension and viscosity, the selectedpigment or dye, drying time of the ink jet ink, and the type of paperonto which the ink will be printed. Representative examples ofwater-miscible co-solvents that may be selected include (1) alcohols,such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropylalcohol, n-butyl alcohol, sec-butyl alcohol, t-butyl alcohol, iso-butylalcohol, furfuryl alcohol, and tetrahydrofurfuryl alcohol; (2) ketonesor ketoalcohols such as acetone, methyl ethyl ketone and diacetonealcohol; (3) ethers, such as tetrahydrofuran and dioxane; (4) esters,such as ethyl acetate, ethyl lactate, ethylene carbonate and propylenecarbonate; (5) polyhydric alcohols, such as ethylene glycol, diethyleneglycol, triethylene glycol, tetraethylene glycol, propylene glycol,polyethylene glycol, glycerol, 2-methyl-2,4-pentanediol1,2,6-hexanetriol and thioglycol; (6) lower alkyl mono- or di-ethersderived from alkylene glycols, such as ethylene glycol mono-methyl (or-ethyl) ether, diethylene glycol mono-methyl (or -ethyl) ether,diethylene glycol mono-butyl (or -ethyl) ether, propylene glycolmono-methyl (or -ethyl) ether, poly(ethylene glycol) butyl ether,triethylene glycol mono-methyl (or -ethyl) ether and diethylene glycoldi-methyl (or -ethyl) ether; (7) nitrogen containing cyclic compounds,such as pyrrolidone, N-methyl-2-pyrrolidone, and1,3-dimethyl-2-imidazolidinone; and (8) sulfur-containing compounds suchas dimethyl sulfoxide, 2,2′-thiodiethanol, and tetramethylene sulfone.

[0031] Typically, the amount of aqueous carrier employed is in the rangeof approximately 70 to 98 weight %, preferably approximately 90 to 98weight %, based on the total weight of the ink. A mixture of water and apolyhydric alcohol, such as diethylene glycol, is useful as an aqueouscarrier. In a preferred embodiment, the inks contain from about 5 toabout 60 weight % of water miscible organic solvent. Percentages arebased on the total weight of the aqueous carrier.

[0032] Other additives which may optionally be present in the ink jetink compositions include thickeners, conductivity enhancing agents,anti-kogation agents, drying agents, waterfast agents, dye solubilizers,chelating agents, binders, light stabilizers, viscosifiers, bufferingagents, anti-mold agents, anti-curl agents, stabilizers and defoamers.Additionally, the ink compositions can include a humectant, asurfactant, a penetrant, a biocide, etc. as is required depending on theapplication.

[0033] A humectant is usually employed in the ink jet compositions ofthe invention to help prevent the ink from drying out or crusting in theorifices of the printhead. Examples of humectants which can be usedinclude polyhydric alcohols, such as ethylene glycol, diethyleneglycol(DEG), triethylene glycol, propylene glycol, tetraethylene glycol,polyethylene glycol, glycerol, 2-methyl-2,4-pentanediol,2-ethyl-2-hydroxymethyl-1,3-propanediol(EHMP), 1,5 pentanediol,1,2-hexanediol, 1,2,6-hexanetriol and thioglycol; lower alkyl mono- ordi-ethers derived from alkylene glycols, such as ethylene glycolmono-methyl or mono-ethyl ether, diethylene glycol mono-methyl ormono-ethyl ether, propylene glycol mono-methyl or mono-ethyl ether,triethylene glycol mono-methyl, mono-ethyl or mono-butyl ether (TEGMBE),diethylene glycol di-methyl or di-ethyl ether, poly(ethylene glycol)monobutyl ether (PEGMBE), and diethylene glycol monobutylether(DEGMBE);nitrogen-containing compounds, such as urea, 2-pyrrolidinone,N-methyl-2-pyrrolidinone, and 1,3-dimethyl-2-imidazolidinone; andsulfur-containing compounds such as dimethyl sulfoxide andtetramethylene sulfone, etc.

[0034] Preferred humectants for the inks of the invention include DEG,glycerol, DEGMBE, TEGMBE, 1,2-hexanediol, 1,5-pentanediol, urea,2-pyrrolidinone, EHMP and mixtures thereof. The humectant may beemployed in each ink in an amount of from about 5 to about 60 weightpercent.

[0035] Surfactants may be added to the ink to adjust the surface tensionto an appropriate level. The surfactants may be anionic, cationic,amphoteric or nonionic and used at levels of 0.01 to 1% of the inkcomposition. Preferred surfactants include Surfynol® 465 (available fromAir Products Corp.) and Tergitol® 15-S-5 (available from Union Carbide).

[0036] A penetrant (0-10% by weight) may also be added to the inkcomposition employed in the process of the invention to help the inkpenetrate the receiving substrate, especially when the substrate is ahighly sized paper. Examples of such penetrants include alcohols, suchas methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol,n-butyl alcohol, sec-butyl alcohol, t-butyl alcohol, iso-butyl alcohol,furfuryl alcohol, and tetrahydrofurfuryl alcohol; ketones orketoalcohols such as acetone, methyl ethyl ketone and diacetone alcohol;ethers, such as tetrahydrofuran and dioxane; and esters, such as, ethyllactate, ethylene carbonate and propylene carbonate.

[0037] A biocide may be added to the ink composition employed in theinvention to suppress the growth of microorganisms such as molds, fungi,etc. in aqueous inks. A preferred biocide for the ink compositionemployed in the present invention is Proxel® GXL (Avecia Corp.) at afinal concentration of 0.0001-0.5 wt. %.

[0038] The pH of the aqueous ink compositions employed in the inventionmay be adjusted by the addition of organic or inorganic acids or bases.Useful inks may have a preferred pH of from about 2 to 10, dependingupon the type of dye being used. Typical inorganic acids includehydrochloric, phosphoric and sulfuric acids. Typical organic acidsinclude methanesulfonic, acetic and lactic acids. Typical inorganicbases include alkali metal hydroxides and carbonates. Typical organicbases include ammonia, triethanolamine (TEA) andtetramethylethlenediamine.

[0039] A film forming polymeric resin may be added to the inkcomposition, to improve the wet and dry rub resistance of the printedimages. Preferably, the film forming polymeric resin is waterdispersible. The polymer used in this invention are generallyhydrophobic polymers of any composition that can be stabilized in awater-based medium. Such hydrophobic polymers are generally classifiedas either condensation polymer or addition polymers. Condensationpolymers include, for example, polyesters, polyamides, polyurethanes,polyureas, polyethers, polycarbonates, polyacid anhydrides, and polymerscomprising combinations of the above-mentioned types. Addition polymersare polymers formed from polymerization of vinyl-type monomersincluding, for example, allyl compounds, vinyl ethers, vinylheterocyclic compounds, styrenes, olefins and halogenated olefins,ethylenically unsaturated carboxylic acids and esters derived from them,unsaturated nitriles, vinyl alcohols, acrylamides and methacrylamides,vinyl ketones, multifunctional monomers, or copolymers formed fromvarious combinations of these monomers.

[0040] Preferred film forming polymeric resin includes thosestyrene/acrylic polymers prepared by free-radical polymerization ofvinyl monomers in aqueous emulsion, polyester ionomers such as EastmanAQ® polyesters, (Eastman Chemical Company) including Eastman PolyestersAQ 29, AQ 38, and AQ 55, and polyurethanes, such as those disclosed inU.S. patent application, Ser. No.09/548,514, filed Apr. 13, 2000, ofYacobucci et al., the disclosure of which is hereby incorporated byreference, Witcobond® polyurethane dispersion by Witco Corp. andSancure® polyurethane by BF Goodrich Company.

[0041] The film forming polymeric resin used in element of the inventionis present in the composition in any effective amount, generally fromabout 0.1 to about 10% by weight, and preferably from about 0.5% toabout 5% by weight.

[0042] The ink can further comprise non film-forming particles,including polymer particles and inorganic particles such as silica,alumina, titanium dioxide, clay, calcium carbonate, barium sulfate, orzinc oxide. It is preferred that the polymer particles have a glasstransition temperature greater than 60° C. More preferably, the polymershould have a glass transition temperature greater than 80° C.

[0043] The non-film forming particles used in element of the inventionis present in the composition in any effective amount, generally fromabout 0.1 to about 10% by weight, and preferably from about 0.5% toabout 5% by weight. The mean particles size of the non-film formingparticles used in the invention is generally in the range of 0.01 to 1micron, more preferably 0.03 to 0.5 micron.

[0044] Most of the ink receiving element commonly used in ink jetprinting can be used in this invention. The support for theink-receiving element employed in the invention can be paper orresin-coated paper, plastics such as a polyolefin type resin or apolyester-type resin such as poly(ethylene terephthalate), polycarbonateresins, polysulfone resins, methacrylic resins, cellophane, acetateplastics, cellulose diacetate, cellulose triacetate, vinyl chlorideresins, poly(ethylene naphthalate), polyester diacetate, various glassmaterials, etc. or comprising an open pore structure such as those madefrom polyolefins or polyesters. The thickness of the support employed inthe invention can be, for example, from about 12 to about 500 μm,preferably from about 75 to about 300 The ink-receiving layer employedin the invention can consist of hydrophilic polymer which is capable ofabsorbing and retaining an ink or can be porous layer havinginterconnecting voids. In a preferred embodiment, the hydrophilicpolymer which may be used in the invention includes poly(vinyl alcohol),poly(vinyl pyrrolidone), gelatin, cellulose ethers, poly(oxazolines),poly(vinylacetamides), partially hydrolyzed poly(vinyl acetate/vinylalcohol), poly(acrylic acid), poly(acrylamide), poly(alkylene oxide),sulfonated or phosphated polyesters and polystyrenes, casein, zein,albumin, chitin, chitosan, dextran, pectin, collagen derivatives,collodian, agar-agar, arrowroot, guar, carrageenan, tragacanth, xanthan,rhamsan and the like. Preferably, the hydrophilic polymer is poly(vinylalcohol), hydroxypropyl cellulose, carboxymethyl cellulose,hydroxypropyl methyl cellulose, a poly(alkylene oxide), poly(vinylpyrrolidinone), or copolymers thereof or gelatin. In another preferredembodiment, the porous ink-receiving layer may contain inorganicparticles such as silica, alumina, titanium dioxide, clay, calciumcarbonate, barium sulfate, or zinc oxide. In an additional preferredembodiment, the porous ink-receiving layer comprises from about 20 % toabout 95 % inorganic particles and from about 5 % to about 80 %polymeric binder, such as gelatin, poly(vinyl alcohol), poly(vinylpyrrolidinone) or poly(vinyl acetate) and copolymers thereof. The porousink-receiving layer can also contain polymer micro-porous structureswithout inorganic filler particles as shown in U.S. Pat. Nos. 5,374,475and 4,954,395.

[0045] The following example illustrates the utility of the presentinvention.

EXAMPLES

[0046] Preparation of Pigment Dispersion

[0047] Cyan Pigment Dispersion

[0048] The cyan pigment dispersion contains: 8000 g of Polymeric beads,mean diameter of 50 μm (milling media); 1600 g of Bridged aluminumphthalocyanine pigment (Eastman Kodak); 960 g of Oleoyl methyl taurine,(OMT) Potassium salt and 5440 g of Deionized water.

[0049] The above components were milled in a 40 liter double walledvessel obtained from BYK-Gardner using a high energy media millmanufactured by Morehouse-Cowles Hochmeyer. The mill was run forapproximately 8 hours at room temperature. During the milling process,three batches of pigment samples (15.0 g each) as PC-1, PC-2, and PC-3were obtained such that the median pigment particle sizes are about 30nm, 100 nm and 150 nm as measured by MICROTRAC II Ultrafine particleanalyzer (UPA) manufactured by Leeds & Northrup. The medium particlesize represents that 50% of the volume in the sample is smaller than theindicated size. The dispersion was separated from the milling media byfiltering the mill grind through a 4-8 μm KIMAX® Buchner Funnel obtainedfrom VWR Scientific Products. Additional 8000 g of dilution water wasadded to the filtered dispersion followed by a biocide, Proxel® GXL(Zeneca Corp.). The pigment is about 10.0% by weight of the total finaldispersion and the biocide is about 230 ppm by weight of the total finaldispersion.

[0050] Yellow Pigment Dispersion

[0051] This dispersion was prepared the same as the Cyan PigmentDispersion 1 except that Pigment Yellow 155 (Clariant Corp.) was usedinstead of Bridged aluminum phthalocyanine pigment. The amount of OMTPotassium salt was 25 weight % based on the pigment. During the millingprocess, four batches of pigment samples (15.0 g each) as PY-1, PY-2,PY-3 and PY-4 were obtained such that the median pigment particle sizesare about 40 nm, 110 nm, 130 nm and 160 nm as measured as measured byMICROTRAC II Ultrafine particle analyzer (UPA) manufactured by Leeds &Northrup.

[0052] Ink-Y1

[0053] To prepare the Ink-Y1, 2.5 g of Pigment Dispersion PY-1 (10%active), 0.05 g Surfynol(t 465 (Air Products Inc.), 0.8 g glycerol, 1.0g triethylene glycol and 0.3 g di(propyleneglycol) methyl ether(Dowanol® DPM), and 0.33 g of AQ55® (30.5% active) were added togetherwith distilled water so that the final weight of the ink was 10.0 g. Thefinal ink contained 2.5% Pigment Yellow 155, 0.50% Surfynol® 465, 8.0%glycerol, 10.0% triethylene glycol, 3% di(propyleneglycol) methyl etherand 1% AQ55®. The solution was filtered through a 3 μmpolytetrafluoroethylene filter and filled into an empty Epson 660 inkjet cartridge.

[0054] Ink-Y1a

[0055] Ink Y1a was prepared similar to Ink-Y1 except that 0.4 g NyacolIJ200® (50% active), a silica dispersion from Akzo-Nobel, was also addedin addition to the other components so that the final ink contained 2%by weight of Nyacol IJ200®.

[0056] Ink-Y1b

[0057] Ink Y1b was prepared similar to Ink-Y1 except that 0.48 g SnowtexST-ZL® (41.5% active), a silica dispersion from Nissan ChemicalIndustry, was also added in addition to the other components so that thefinal ink contained 2% by weight of Snowtex ST-ZL®.

[0058] Ink-Y1c

[0059] Ink Y1c was prepared similar to Ink-Y1 except that 0.5 g EF10611® (40% active), a silica dispersion from Akzo-Nobel, was also addedin addition to the other components so that the final ink contains 2% byweight of EF10611®.

[0060] Ink-Y2

[0061] Ink Y2 was prepared similar to Ink-Y1 except that pigmentdispersion PY-2 was used instead of pigment dispersion PY-1.

[0062] Ink-Y3

[0063] Ink Y3 was prepared similar to Ink-Y1 except that pigmentdispersion PY-3 was used instead of pigment dispersion PY-1.

[0064] Ink-Y4

[0065] Ink Y4 was prepared similar to Ink-Y1 except that pigmentdispersion PY-4 was used instead of pigment dispersion PY-1.

[0066] Ink-Y5

[0067] Ink Y5 was obtained from the yellow channel of Epson 2000P ColorCartridges, CAT. No.T106201. The ink was then refilled into an Epson 660empty cartridge.

[0068] Ink-Y6

[0069] Ink Y6 was obtained from Epson C80 yellow cartridges, CAT.No.T032420. The ink was then refilled into an Epson 660 empty cartridge.

[0070] Ink-C1

[0071] Ink C1 was prepared similar to Ink-Y1 except that 2.2 g bridgedaluminium phthalocyanine pigment dispersion PC-1 (10% active) was usedinstead of pigment dispersion PY-1. The final ink contained 2.2% byweight of bridged aluminium phthalocyanine pigment.

[0072] Ink-C1a

[0073] Ink C1a was prepared similar to Ink-C1 except that 0.4 g NyacolIJ200® (50% active), a silica dispersion from Akzo-Nobel, was also addedin addition to the other components so that the final ink contained 2%by weight of Nyacol IJ200®.

[0074] Ink-C1b

[0075] Ink C1b was prepared similar to Ink-C1 except that 0.48 g SnowtexST-ZL® (41.5% active), a silica dispersion from Nissan ChemicalIndustry, was also added in addition to the other components so that thefinal ink contained 2% by weight of Snowtex ST-ZL®.

[0076] Ink-C1c

[0077] Ink C1c was prepared similar to Ink-C1 except that 0.5 g EF10611®(40% active), a silica dispersion from Akzo-Nobel, was also added inaddition to the other components so that the final ink contained 2%weight of EF10611®.

[0078] Ink-C2

[0079] Ink C2 was prepared similar to Ink-C1 except that pigmentdispersion PC-2 was used instead of pigment dispersion PC-1.

[0080] Ink-C3

[0081] Ink C3 was prepared similar to Ink-C1 except that pigmentdispersion PC-3 was used instead of pigment dispersion PC-1.

[0082] Ink-C4

[0083] Ink C4 was obtained from the dark cyan channel of Epson 2000PColor Cartridges, CAT. No.T106201. The ink was then refilled into anEpson 660 empty cartridge.

[0084] Ink-C5

[0085] Ink C5 was obtained from Epson C80 cyan cartridges, CAT.No.T032220, the ink was then refilled into an Epson 660 empty cartridge.

[0086] Ink-M1

[0087] Ink M1 was obtained from the dark magenta channel of Epson 2000PColor Cartridges, CAT. No.T106201. The ink was then refilled into anEpson 660 empty cartridge.

[0088] Ink-M2

[0089] Ink M2 was obtained from Epson C80 magenta cartridges, CAT.No.T032320. The ink was then refilled into an Epson 660 empty cartridge.

[0090] Comparative Ink Set 1 (Comp-1)

[0091] Inks-C5, M2, and Y6 were used as a set of cyan, magenta, andyellow, and filled into the C, M, Y Channels of an Epson 660 empty Colorcartridges, respectively.

[0092] Comparative Ink Set 2 (Comp-2)

[0093] Inks-C4, M1, Y5 were used as a set of cyan, magenta and yellow,and filled into the C, M, Y Channels of an Epson 660 empty Colorcartridges, respectively.

[0094] Ink Set-1 of the Invention (I-1)

[0095] Inks-C1, M1, Y2 were used as a set of cyan, magenta and yellow,and filled into the C, M, Y Channels of an Epson 660 empty Colorcartridges, respectively.

[0096] Ink Set -2 of the Invention (I-2)

[0097] Inks-C2, M2, Y3 were used as a set of cyan, magenta and yellow,and filled into the C, M, Y Channels of an Epson 660 empty Colorcartridges, respectively.

[0098] Particle Size Measurement

[0099] All particles were characterized by MICROTRAC II Ultrafineparticle analyzer (UPA) manufactured by Leeds & Northrup. The datareported are the size that 50% of the volume in the sample that issmaller than the indicated size, which is also known as the mediandiameter.

[0100] Printing and Evaluation

[0101] Elements were prepared using test images consisting of cyan,magenta, yellow, red, green and blue single color patches ofapproximately 3 by 3 centimeters in size with a Dmax density (100% dotcoverage). Using an Epson 660 inkjet printer loaded with the abovecolored inks, the above test images were printed onto commerciallyavailable Epson Premium Glossy Paper, Cat. No SO41286 (The 60° glosslevel of this receiver is about 34). The elements were allowed to dryfor 24 hours at ambient temperature and humidity. Using the BYK-Gardnermicro-TRI-glossmeter, gloss level from each patch was measured at 60°specular angle. Multiple measurements were carried out using threeindividual patches of the same color and the average values were used inthe following tables. TABLE 1 Gloss Adjustment By Pigment Particle SizeMean Pigment Particle Size at Ink 50% (nm) 60° Gloss Y1 40 109 Y2 110 93Y3 130 73 Y4 160 50 Y5 57 96 Y6 15 106 M1 81 85 M2 120 66 C1 30 89 C2100 62 C3 150 47 C4 90 65 C5 81 62

[0102] TABLE 2 Gloss Adjustment by Non-film forming Particles in inkMean Pigment Non-film Mean Additive Particle Size at Forming ParticleSize at 60° Ink 50% (nm) Additive 50% (nm) Gloss Y1 40 — — 109 Y1a 40Nyacol ™ IJ200  77 91 Y1b 40 Snowtex ™ ST-ZL 120 86 Y1c 40 EF10611 15079 C1 30 — — 89 C1a 30 Nyacol ™ IJ200  77 78 C1b 30 Snowtex ™ ST-ZL 12075 C1c 30 EF10611 150 70

[0103] TABLE 3 Pigment Ink Set Selection Inks 60 degree gloss on colorpatches RGV Ink Set C M Y C M Y R G B AG % Comp-1 C5 M2 Y6 62 66 106 7373 64 74 15 Comp-2 C4 M1 Y5 65 85 96 78 50 46 70 23 I-1 C1 M1 Y2 82 8193 84 92 76 85 6 I-2 C2 M2 Y3 62 66 73 70 69 72 69 5

[0104] Table 1 showed that the gloss levels of printed elements from thepigment based inks can be adjusted by using pigments of differentparticle sizes. The bigger the particle sizes, the lower the gloss valueof the printed elements. Table 2 showed that the gloss levels of theprinted elements of the pigment inks can be adjusted by adding anon-film forming particle additive. When using the same pigmentdispersion, the bigger the size of the non-film forming additive, thelower the gloss of the printed element. Table 3 showed a comparison ofRelative Gloss Variability (RGV %) calculated based on the gloss levelsof cyan, magenta, yellow, red, green and blue color patches. Comparedwith the comparative examples, the pigment ink set of the presentinvention gave much lower gloss variability.

[0105] The present description will be directed in particular toelements forming part of, or cooperating more directly with, apparatusand methods in accordance with the present invention. It is to beunderstood that elements not specifically shown or described may takevarious forms well known to those skilled in the art.

What is claimed is:
 1. A color set for forming an ink jet imagecomprising: at least two color inks, each ink comprising a carrier and apigment; wherein the Relative Gloss Variability (RGV) (Equation A) amonginks is less than 10% when 60° is used as the specular angle:$\begin{matrix}\begin{matrix}{{{RGV}(\%)} = \frac{\frac{\sum\limits_{I = 1}^{N}{\left( {{{Gloss}\left( {{Imaged}\quad {Area}} \right)}_{I} - {AG}} \right)}}{AG}}{N}} \\{Where} \\{{AG} = \frac{\sum\limits_{I = 1}^{N}{{Gloss}\left( {{Imaged}\quad {Area}} \right)}_{I}}{N}}\end{matrix} & {{Equation}\quad (A)}\end{matrix}$

I is a variable which identifies a certain color patch used in theevaluation, N is the total number of color patches used in theevaluation.
 2. The color set of claim 1 wherein the gloss variability isless than 7%, when 60° is used as the specular angle.
 3. The color setof claim 1 wherein the gloss variability is less than 5%, when 60° isused as the specular angle.
 4. The color set of claim 1 wherein said atleast two color inks are selected from the group consisting of Cyan,Yellow, Magenta, Black, White, Green, Violet and Orange.
 5. The colorset of claim 1 wherein said pigment comprises particles less than 0.5micron in size.
 6. The color set of claim 1 wherein said pigmentrepresents 0.1 to 10 weight % of the ink composition.
 7. The color setof claim 4 wherein the yellow pigment is COLOR INDEX Pigment Yellow 155or COLOR INDEX Pigment Yellow
 74. 8. The color set of claim 4 whereinthe cyan pigment is COLOR INDEX Pigment Blue 15:3 orbis(phthalocyanylalumino)tetraphenyldisiloxane.
 9. The color set ofclaim 4 wherein the magenta pigment is COLOR INDEX Pigment Red
 122. 10.The color set of claim 1 wherein said at least two color inks furthercomprise non-film forming particles.
 11. The color set of claim 10wherein the non-film forming particles range in size from 0.01 to 1micron.
 12. The color set of claim 10 wherein the non-film formingparticles range in size from 0.03 to 0.5 micron.
 13. The color set ofclaim 10 wherein the non-film forming particles are inorganic particles.14. The color set of claim 13 wherein the inorganic particles comprisesilica, alumina, titinium dioxide, zirconia and clay, calcium carbonate,barium sulfate, zinc oxide, or combinations thereof.
 15. The color setof claim 13 wherein the inorganic particles comprise silica.
 16. Thecolor set of claim 10 wherein the said non-film forming particles areorganic polymeric particles.
 17. The color set of claim 16 wherein theorganic polymeric particles comprise a polyurethane, a polyacrylic, or apolyester, each with a Tg of greater than 60° C.
 18. The color set ofclaim 1 further comprising a film forming polymer resin.
 19. The colorset of claim 18 wherein the film forming polymer resin is a polyester, apolyurethane or a polyacrylic.
 20. The color set of claim 18 wherein thefilm forming polymer resin is a sulfonated polyester ionomer.
 21. Thecolor set of claim 1 imagewise disposed on a receiver.